Microphones in conventional MEMS (Micro-Electro-Mechanical System) is generally formed by stack-based growing of a backplate and a diaphragm etc. on the base through a process of chemical vapor deposition. There is a stepped structure at an edge of the backplate in this structure. The stepped structure is arched towards a direction facing away from the base, so that a receiving space for receiving the diaphragm can be left between the backplate and the base.
The inventors of the present disclosure have found at least the following problems exist in the related art. At present, since the material of the backplate is silicon nitride, in the process of chemical vapor deposition for the backplate, a region where the density decreases due to a difference in growth rate of silicon nitride occurs in the vicinity of the stepped structure. During etching the silicon nitride by an etching solution, the chemical solution will excessively erode the area where the density is lowered, causing a crack in this area of the backplate, thereby weakening the strength of the backplate. Therefore, the stepped portion becomes the weakest in the entire structure of the backplate. During processes of dropping, blowing, etc., an external airflow rushes into a back chamber, the elastic diaphragm is pushed to move toward the backplate, and the diaphragm transfers the pressure to the backplate by contacting with the backplate, causing the backplate to be broken at the fragile stepped portion, further causing damage to the microphone structure, and resulting in low reliability of the microphone.